A structure and construction method for an ultra-long approach slab in a high-fill roadbed

Abstract

This invention discloses a structure and construction method for an ultra-long approach slab in high-fill roadbeds, applicable to the design and construction of bridge approach slabs in high-fill roadbeds. The structure consists of three parts: a two-way prestressed concrete slab, a reinforced concrete slab, and connecting joints. The invention also discloses a construction method for the ultra-long approach slab, including: prefabrication of the two-way prestressed concrete slab and reinforced concrete slab; tensioning and grouting of the two-way prestressed concrete slab; slab installation; and construction of the transverse self-stressing joint and the longitudinal hinged connecting joint. The structure and construction method disclosed in this invention feature segmented design, factory prefabrication, on-site installation, and connecting joint connection, offering advantages over traditional reinforced concrete approach slabs such as reasonable overall stress distribution, seamless operation, economic efficiency, safety, and longer service life.

Description

Technical Field

[0001] This invention relates to the field of bridge structure and construction technology, and in particular to a structure and construction method for an ultra-long approach slab in a high-fill roadbed. Background Technology

[0002] Bridge approach slab settlement in high-fill roadbeds has always been a difficult problem in highway construction. To solve the problem of bridge approach slab settlement caused by uneven settlement between the bridge and the high-fill roadbed at the bridge approach, a common and effective solution is to increase the length of the approach slab to reduce the slope between the high-fill roadbed and the abutment. Traditional cast-in-place reinforced concrete extra-long approach slabs are designed to be thick and have a large amount of reinforcement, which is very uneconomical. If cast-in-place prestressed concrete approach slabs are used, since there is no space between the approach slab and the abutment for operating prestressing tensioning equipment, they must be prefabricated in a precast plant, tensioned and grouted in the precast plant, and then installed on site. Due to the long design of the approach slab and the limited space at the bridge approach, the installation of extra-long approach slabs is extremely unsafe, and the approach slabs on the side farther from the abutment have less stress and require more reinforcement, resulting in unnecessary waste. This invention relates to a structure and construction method for an ultra-long approach slab in a high-fill roadbed. As vehicles continue to move, the approach slab becomes suspended due to roadbed settlement at the base layer near the bridge abutment end. The bending moment of the suspended portion of the approach slab is relatively large. The portion of the approach slab away from the bridge abutment end settles together with the roadbed, thus preventing the approach slab from becoming suspended and resulting in a smaller bending moment. The extra-long approach slab of this invention adopts a segmented design. Near the abutment end, due to the larger suspended bending moment, a two-way prestressed concrete slab design is used, which has greater stiffness, less reinforcement, and thinner slab thickness than traditional cast-in-place reinforced concrete approach slabs. Further away from the abutment end, where there is no suspension and smaller deflection, a reinforced concrete slab design is used. The two-way prestressed concrete slabs are connected to the reinforced concrete slabs by self-stressing joints. These self-stressing joints themselves have a certain self-stress. During the pouring process, the high-expansion concrete expands while simultaneously applying a gradually decreasing compressive stress to the reinforced concrete slab end. This solves both the problem of insufficient overall strength in ordinary wet joints and the problem of uniform longitudinal transition from stress to stress-free conditions in the approach slab. Simultaneously, a longitudinal hinged connection joint is set between the left and right slabs, allowing only shear force to be transferred between them, not bending moment. The stress distribution of the slab is clearly defined, and the transverse reinforcement of the left and right slabs is greatly reduced. This invention features factory prefabrication and on-site installation. The overall segmented design of the approach slab results in reasonable overall stress distribution, seamless operation, thinness, economy, safety, and longer service life. Summary of the Invention

[0003] The technical problem to be solved by this invention is that the design thickness of the extra-long cast-in-place reinforced concrete slab is relatively large and the reinforcement is too much, which is extremely uneconomical; the extra-long prestressed concrete slab cannot be cast in place, and if it is prefabricated in the factory and installed on site, the construction is extremely inconvenient and unsafe.

[0004] To address the aforementioned problems, this invention provides a structure and construction method for a long approach slab in a high-fill roadbed. The slab is prefabricated in a factory and installed on-site. The approach slab is designed with segmented sections, resulting in a rational overall stress distribution. The structure consists of three parts: a two-way prestressed concrete slab, a reinforced concrete slab, and connecting joints.

[0005] A two-way prestressed concrete slab consists of concrete, two longitudinal layers of prestressed tendons, and a single transverse layer of prestressed tendons.

[0006] Reinforced concrete slabs consist of concrete and two layers of secondary steel bars arranged longitudinally and transversely.

[0007] The joint consists of a transverse self-stressing joint and a longitudinal hinged joint.

[0008] The arrangement of the three parts constituting the approach slab is as follows: two bidirectional prestressed concrete slabs are set near the abutment end, with the width and thickness of the two reinforced concrete slabs being the same as the width and thickness of the corresponding bidirectional prestressed concrete slabs in the longitudinal direction, and set away from the abutment end; the bidirectional prestressed concrete slabs and ordinary reinforced concrete slabs are connected and transitioned by transverse self-stressing joints; the bidirectional prestressed concrete slabs and reinforced concrete slabs are connected by longitudinal hinged joints; the transverse self-stressing joints and longitudinal hinged joints are characterized in that the longitudinal hinged joints are continuous throughout the entire approach slab, and the two transverse self-stressing joints are spaced apart at the intersection with the longitudinal hinged joints.

[0009] According to a preferred embodiment of the present invention, the center line of the longitudinal hinged joint coincides with the position of the marking provided on the approach slab between the driving lane and the overtaking lane; the position of the transverse self-stressing joint matches the length of the bidirectional prestressed concrete slab.

[0010] According to another preferred embodiment of the present invention, the length of the slab matches the expected suspended length of the highway under the slab within its design life. The slab is 7m-8m long, 4.20m-6.70m wide, and 25cm-40cm thick, with a concrete grade of 40MPa-45MPa. The slab has double rows of symmetrical prestressing tendons in its longitudinal direction and a single row of prestressing tendons in the middle of its transverse direction. The transverse spacing of the longitudinal prestressing tendons is 30cm-60cm, and the longitudinal spacing of the transverse prestressing tendons is 50cm-70cm.

[0011] According to another preferred embodiment of the present invention, the slab is 4m-6m long, 4.20m-6.70m wide, and 25cm-40cm thick, with a concrete grade of 40MPa-45MPa. The upper layer is longitudinally reinforced with secondary steel bars of 16mm-18mm in diameter and spaced 15cm-18cm in the transverse direction. The lower layer is longitudinally reinforced with secondary steel bars of 22mm-25mm in diameter and spaced 15cm-18cm in the transverse direction. Both the upper and lower layers are reinforced with secondary steel bars of 16mm-18mm in diameter and spaced 20cm-25cm in the longitudinal direction.

[0012] According to another preferred embodiment of the present invention, the self-stressing joint is composed of high-expansion concrete, longitudinal self-stressing tendons, and transverse self-stressing joint reinforcement, with a joint width of 22cm-30cm. The high-expansion concrete has the same grade as the slab concrete, which is 40MPa-45MPa. The self-stressing tendons are symmetrical HRB335 steel bars arranged in the upper and lower layers within the self-stressing joint, which are respectively embedded in the bidirectional prestressed concrete slab and the reinforced concrete slab.

[0013] According to another preferred embodiment of the present invention, the diameter of the reinforcing bar is 16mm-18mm, the transverse spacing of the reinforcing bar is 15cm-18cm, the transverse reinforcing bar is a double row of grade II reinforcing bars arranged transversely in the self-stressing joint, the upper and lower transverse reinforcing bars are tied to the self-stressing reinforcing bar at equal intervals, and the diameter of the reinforcing bar is 12mm-14mm; the dosage of high-efficiency expansion agent in the high-expansion concrete is 10%-12%.

[0014] According to another preferred embodiment of the present invention, the embedded length in the bidirectional prestressed concrete slab and the reinforced concrete slab is 48cm-54cm, the exposed length is 18cm-24cm, and the protective layer thickness of the embedded self-stressing tendon is not less than 7cm.

[0015] According to another preferred embodiment of the present invention, the longitudinal hinged joint is composed of four parts: micro-expansion concrete, tie rod, anti-rust coating, and pre-cut joint. The joint width is 12cm-15cm, and the micro-expansion concrete grade is 40MPa-45MPa. The tie rod is embedded in the bidirectional prestressed concrete slab and the reinforced concrete slab, and the embedded position is located in the middle of the slab. The anti-rust coating is located in the middle of the tie rod. The pre-cut joint is located on the center line of the longitudinal hinged joint.

[0016] According to another preferred embodiment of the present invention, grade II steel bars with a diameter of 20cm-22cm are used, with a pre-embedded length of 60cm-66cm and an exposed length of 8cm-12cm, and the longitudinal spacing of the steel bars is 50cm-55cm; the anti-rust coating is located in the middle 8cm-10cm portion of the tie bar; the expansion agent content in the micro-expansion concrete is 5%-8%; the longitudinal hinged connection joint has a pre-cut joint with a width of 1cm-1.5cm and a depth of 4cm-5cm at its center, and the joint is filled with petroleum asphalt.

[0017] According to another aspect of the present invention, a construction method for an ultra-long approach slab structure in a high-fill roadbed is provided, characterized in that the method includes the following steps:

[0018] 1) Precasting: The steel formwork for the two-way prestressed concrete slab and the reinforced concrete slab is erected separately according to the dimensions of the left and right sides; the longitudinal and transverse corrugated pipes of the two-way prestressed concrete slab and the longitudinal and transverse double-layer steel bars of the reinforced concrete slab are fixed, and the longitudinal self-stressing tendons and transverse tie bars are embedded; the concrete is poured, vibrated with a vibrator, and the surface is finished with a grinder; the surface is covered with curing cloth and watered for seven days.

[0019] 2) Tensioning and grouting of bidirectional prestressed concrete slabs: When the concrete strength of the slab reaches 100% of the design strength, steel strands are inserted into the corrugated pipes; the steel strands are tensioned to the design value; cement concrete grout is injected into the corrugated pipes; and the anchors are sealed.

[0020] 3) Installation: Lay a double layer of tar paper on the corbel, and install the two-way prestressed concrete slab and reinforced concrete slab in sequence according to the reserved position of the joint; install anchor bolts to anchor the slab to the corbel.

[0021] 4) Construction of transverse self-stressing joint: Connect longitudinal self-stressing tendons, with a welding length of not less than 10 times the diameter, and tie transverse reinforcing bars; pour high-expansion concrete and water-cur for seven days;

[0022] 5) Construction of longitudinal hinged joint: Connect the transverse tie rods, and weld the length on both sides not less than 5 times the diameter; apply anti-rust coating at 8cm-10cm in the middle of the tie rods, pour micro-expansion concrete, and cure with moisturizing cotton for seven days; use a concrete cutter to cut a pre-cut joint at the center line of the longitudinal hinged joint, and inject petroleum asphalt.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1) The extra-long approach slab of the present invention is designed in sections according to the stress conditions. The end near the abutment adopts a two-way prestressed concrete slab design, which has greater rigidity, less reinforcement, thinner slab thickness, and seamless operation than the traditional cast-in-place reinforced concrete approach slab. The end away from the abutment adopts a reinforced concrete slab design.

[0025] 2) This invention uses a transverse self-stressing joint to connect the two-way prestressed concrete slab and the reinforced concrete slab. The transverse self-stressing joint itself has a certain self-stress. During the pouring of the self-stressing joint, the high-expansion concrete expands and at the same time, it gives the ordinary concrete slab end a compressive stress that gradually decreases from near to far. This can solve the problem of insufficient overall strength of ordinary connection joints and also solve the problem of uniform transition from stress to no stress in the longitudinal direction of the slab.

[0026] 3) The longitudinal hinged joint of the present invention connects the left and right precast slabs. Only shear force is transmitted between the left and right slabs, not bending moment. The stress on the slab is clear, and the transverse reinforcement of the left and right slabs is greatly reduced. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the planar structure of the present invention;

[0028] Figure 2 This is a schematic diagram of section II;

[0029] Figure 3 This is a schematic diagram of section II-II;

[0030] Figure 4 This is a schematic diagram of section III-III;

[0031] The relevant labels in the figure are as follows:

[0032] 1. Abutment; 2. Corbel; 3. Two-way stress concrete left slab; 4. Two-way stress concrete right slab; 5. Reinforced concrete left slab; 6. Reinforced concrete right slab; 7. Longitudinal hinged joint; 8. Pre-cut joint; 9. Transverse self-stressing joint; 10. Driving lane; 11. Overtaking lane; 12. Tie bar; 13. Upper longitudinal reinforcement of reinforced concrete slab; 14. Lower longitudinal reinforcement of reinforced concrete slab; 15. Upper transverse reinforcement of reinforced concrete; 16. Lower transverse reinforcement of reinforced concrete; 17. Micro-expansion concrete; 18. High-expansion concrete; 19. Upper longitudinal stress reinforcement; 20. Lower longitudinal stress reinforcement; 21. Transverse prestressing reinforcement; 22. Self-stressing reinforcement; 23. Transverse reinforcement of self-stressing joint; 24. Petroleum asphalt; 25. Anti-rust coating. Implementation

[0033] To address the issue of bridge approach slab settlement caused by uneven settlement between the bridge and the high-fill subgrade, one common solution is to lengthen the approach slab to reduce the slope between the high-fill subgrade and the abutment. Traditional cast-in-place reinforced concrete approach slabs, however, are uneconomical due to their thicker design and larger reinforcement requirements for longer slabs. Therefore, a structure and construction method for ultra-long approach slabs in high-fill subgrades have been invented, applicable to the design and construction of such slabs.

[0034] The following will combine Figure 1-4The structure of the ultra-long approach slab for high-fill roadbed described in this invention is described in detail.

[0035] like Figure 1 , Figure 2 As shown, the structure is characterized by consisting of three parts: a two-way prestressed concrete slab (3) and (4), a reinforced concrete slab (5) and (6), and a connecting joint (7) and (9).

[0036] The two-way prestressed concrete slab (3) and (4) are composed of longitudinal prestressed tendons (19) and (20) in the upper and lower layers of concrete and a single layer of transverse prestressed tendons (21).

[0037] The reinforced concrete slabs (5) and (6) are composed of concrete and secondary steel bars in the upper longitudinal and transverse (13) and (15) layers and the lower longitudinal and transverse (14) and (16) layers.

[0038] The joint consists of a transverse self-stressing joint (9) and a longitudinal hinged joint (7).

[0039] The arrangement of the three parts of the slab is as follows: the two-way prestressed concrete slab is divided into left (3) and right (4) and is set near the abutment (1). The width and thickness of the left (5) and right (6) reinforced concrete slabs are the same as the width and thickness of the corresponding two-way prestressed concrete slabs in the longitudinal direction and are set away from the abutment (1). The two-way prestressed concrete slabs and ordinary reinforced concrete slabs are connected and transitioned by transverse self-stressing joints (9). The two-way prestressed concrete slabs and the reinforced concrete slabs are connected by longitudinal hinged joints (7).

[0040] like Figure 1 As shown, the transverse self-stressing joint (9) and the longitudinal hinged joint (7) are characterized in that the longitudinal hinged joint (7) is continuous in the longitudinal direction of the entire slab, and the transverse self-stressing joint (9) is spaced apart on the left and right sides at the intersection with the longitudinal hinged joint (7).

[0041] The location of the longitudinal hinged joint (7) is characterized in that the center line of the longitudinal hinged joint (7) coincides with the position of the marking line set between the driving lane (10) and the overtaking lane (11) on the approach slab; the location of the transverse self-stressing joint (9) matches the length of the bidirectional prestressed concrete slab.

[0042] As the roadbed settles, the lower base of the approach slab near the abutment becomes suspended, resulting in a large bending moment in the suspended section. Therefore, a two-way prestressed concrete slab structure is adopted for the suspended section of the approach slab.

[0043] like Figure 2 , Figure 3As shown, the bidirectional prestressed concrete slabs (3) and (4) are designed according to the expected span of 4m-5m of suspended slab, with a slab length of 7m-8m and a designed slab width of 4.20m-6.70m. The preferred width of the left slab (3) is 4.20m, and the preferred width of the right slab (4) is 6.20m and 6.70m. The slab thickness is 25cm-40cm, with preferred thicknesses of 25cm, 30cm, 35cm, and 40cm. The concrete grade is 40MPa-45MPa. The preferred concrete grade is 40 MPa. The upper longitudinal stress tendon (19) and the lower longitudinal stress tendon (20) are set in the longitudinal direction of the slab. A single row of transverse prestressing tendons (21) is set in the middle of the slab. According to the stress condition of the slab, the transverse spacing of the upper and lower longitudinal prestressing tendons (19) and (20) is 30cm-60cm, and the longitudinal spacing of the transverse prestressing tendons (21) is 50cm-70cm. The preferred prestressing tendons are steel strands with a diameter of 15.24mm and a strength grade of 1860 MPa.

[0044] The section of the approach slab away from the abutment settles together with the roadbed, which will not cause the approach slab to be suspended. The bending moment of the approach slab is small, and this section of the approach slab adopts a reinforced concrete slab structure.

[0045] like Figure 3 , Figure 4 As shown, the reinforced concrete slab is designed to be 4m-6m long and 4.20m-6.70m wide. The preferred width of the left side (6) is 4.20m, and the preferred width of the right side (5) is 6.20m and 6.70m. The slab thickness is 25cm-40cm, with the preferred thicknesses being 25cm, 30cm, 35cm, and 40cm. The concrete grade is 40MPa-45MPa, with the preferred concrete grade being 40MPa. The upper longitudinal reinforcement (13) is a grade II steel bar with a diameter of 16mm-18mm, and the lower longitudinal reinforcement (14) is a grade II steel bar with a diameter of 22mm-25mm. The transverse spacing of the upper longitudinal reinforcement (13) and the lower longitudinal reinforcement (14) is the same, both being 15cm-18cm. The upper transverse reinforcement (15) and the lower transverse reinforcement (16) are both grade II steel bars with a diameter of 16mm-18mm, with a longitudinal spacing of 20cm-25cm.

[0046] The approach slab uses a two-way prestressed concrete slab near the abutment and a reinforced concrete slab far from the abutment. If ordinary concrete wet joints are used for connection, the stress change from the prestressed two-way prestressed concrete slab to the stress-free reinforced concrete slab is large, which can easily cause stress concentration and damage to the wet joint. Self-stressing joints are used for connection. The self-stressing joint itself has a certain self-stress. During the pouring of the self-stressing joint, the high-expansion concrete expands and at the same time, it applies a compressive stress to the end of the ordinary concrete slab that gradually decreases from near to far. This can solve the problem of insufficient overall strength of the wet joint and also solve the problem of the longitudinal transition of the approach slab from stress to stress-free.

[0047] The parameters mentioned above are the optimal parameters selected by the inventor through countless experiments and on-site construction results. They are not subjective guesses, but were obtained through countless comparisons, references and continuous changes.

[0048] like Figure 2 As shown, the transverse self-stressing joint structure is characterized by the self-stressing joint being composed of high-expansion concrete (18), longitudinal self-stressing tendons (22), and transverse self-stressing joint reinforcement (23). The joint width is 22cm-30cm. The grade of the high-expansion concrete (18) is the same as that of the slab concrete, which is 40MPa-45MPa. The amount of high-efficiency expansive agent in the expansive concrete is 10%-12%. The longitudinal self-stressing tendon (22) is characterized by being a double-layered symmetrical HRB335 steel bar set in the self-stressing joint, which is pre-embedded in the bidirectional prestressed concrete slab (3) (4) and the reinforced concrete slab (5) (6) respectively. The diameter of the steel bar is 16mm-18mm, and the transverse spacing of the steel bar is 15cm-18cm. The transverse self-stressing joint reinforcement (23) is a double-row of secondary steel bars set in the self-stressing joint, which is tied to the self-stressing tendon (22) at equal intervals. The diameter of the steel bar is 12mm-14mm.

[0049] like Figure 2 As shown, the longitudinal self-stressing tendon (22) is characterized in that it is embedded in the bidirectional prestressed concrete slab (3) (4) and the reinforced concrete slab (5) (6), with an embedded length of 48cm-54cm and an exposed length of 18cm-24cm. The protective layer thickness of the embedded self-stressing tendon (22) is not less than 7cm.

[0050] A longitudinal hinged connection joint is set between the left and right precast slabs. The micro-expansion concrete can prevent cracking at the longitudinal joint and the joint between the left and right slabs caused by drying shrinkage and thermal shrinkage after concrete pouring. If the two-way prestressed concrete slab and reinforced concrete slab are not designed with left and right lanes, the lateral bending moment of the slab is large and the reinforcement is more. This invention uses a longitudinal hinged connection joint design between the driving lane and the overtaking lane. The left and right slabs only transfer shear force and not bending moment, which greatly reduces the lateral bending moment of the left and right precast slabs and correspondingly reduces the amount of reinforcement.

[0051] The parameters mentioned above are the optimal parameters selected by the inventor after countless experiments and on-site construction results. They are not subjective guesses, but were obtained through countless comparisons, references and continuous changes.

[0052] like Figure 3 , Figure 4As shown, the longitudinal hinged joint (7) structure is characterized in that the longitudinal hinged joint (7) is composed of four parts: micro-expansion concrete (17), tie bar (12), anti-rust coating (25) and pre-cut joint (8). The joint width is 12cm-15cm, and the micro-expansion concrete (17) grade is 40mpa-45mpa. The tie bar (12) is embedded in the bidirectional prestressed concrete slab (3) (4) and reinforced concrete slab (5) (6), and the embedded position is located in the middle of the slab (3) (4) (5) (6). The anti-rust coating (25) is located in the middle of the tie bar (12). The pre-cut joint (8) is located on the center line of the longitudinal hinged joint (7).

[0053] The tie bar (12) of the longitudinal hinged joint (7) is characterized by a secondary steel bar with a diameter of 20cm-22cm, a pre-embedded length of 60cm-66cm, an exposed length of 8cm-12cm, and a longitudinal spacing of 50cm-55cm for the tie bar (12); the anti-rust coating (25) is located 8cm-10cm in the middle of the tie bar (12); the expansion agent content in the micro-expansion concrete (17) is 5%-8%; the longitudinal hinged joint (7) has a pre-cut joint (8) with a width of 1cm-1.5cm and a depth of 4cm-5cm in the center, and the joint is filled with petroleum asphalt (24).

[0054] In the entire construction sequence of the slab, the transverse self-stressing joint is constructed first, allowing the high-expansion concrete in the transverse self-stressing joint to fully expand, so that the stress transition between the two-way prestressed concrete slab and the reinforced concrete slab is not affected by the longitudinal hinged connection joint. Then the longitudinal hinged connection joint is constructed.

[0055] The inventor would like to reiterate that the specific data and parameters mentioned above are the optimal parameters selected by the inventor through numerous experiments and on-site construction results. They are not subjective conjectures, but were obtained through numerous comparisons, references, and continuous changes. They are indispensable for the technical contribution to this invention and the specific performance optimization of the product.

[0056] Reference Figure 1 - As shown in Figure 4, the present invention also provides a construction method for the aforementioned high-fill roadbed ultra-long approach slab structure, characterized in that the method includes the following steps:

[0057] 1) Precasting: The steel formwork for the two-way prestressed concrete slabs (3) and (4) and the reinforced concrete slabs (5) and (6) are respectively supported according to the dimensions of the left and right sides; the longitudinal and transverse corrugated pipes of the two-way prestressed concrete slabs (3) and (4) are fixed with the longitudinal and transverse double-layer steel bars (13) (14) (15) (16) of the reinforced concrete slabs (5) and (6), and the longitudinal self-stressing tendons (22) and transverse tie bars (12) are pre-embedded; the concrete is poured, vibrated with a vibrator, and the surface is finished with a grinder; the surface is covered with curing cloth and watered for seven days;

[0058] 2) Tensioning and grouting of bidirectional prestressed concrete slabs (3) and (4): When the concrete strength of the slab reaches 100% of the design strength, prestressing tendons (19), (20), and (21) are inserted into the corrugated pipe; the prestressing tendons (19), (20), and (21) are tensioned to the design value; cement concrete grout is injected into the corrugated pipe; and the anchor is sealed.

[0059] 3) Installation: Lay double-layer tar paper on the corbel (2), and install the bidirectional prestressed concrete slab (3) (4) and reinforced concrete slab (5) (6) in sequence according to the reserved positions of the connecting seam (7) (9); install anchor bolts to anchor the slab to the corbel (2);

[0060] 4) Construction of transverse self-stressing joint (9): Connect longitudinal self-stressing tendons (22), with a welding length of not less than 10 times the diameter, and tie transverse self-stressing joint tendons (23); pour high-expansion concrete (18) and water-cur for seven days;

[0061] 5) Construction of longitudinal hinged joint (7): Connect transverse tie bars (12), with a double-sided welding length of not less than 5 times the diameter; apply anti-rust coating (25) at 8cm-10cm in the middle of the tie bar (12), pour micro-expansion concrete (17), and cure with moisturizing cotton for seven days; use a concrete cutting machine to cut a pre-cut joint (8) at the center line of the longitudinal hinged joint (7), rinse the debris in the cut joint with clean water, dry it with a blower, and inject petroleum asphalt (24).

[0062] The extra-long approach slab of this invention is designed in sections according to the stress conditions. Near the abutment end, a two-way prestressed concrete slab is used, which has greater stiffness, less reinforcement, thinner slab thickness, and seamless construction compared to traditional cast-in-place reinforced concrete approach slabs. Further away from the abutment end, a reinforced concrete slab is used. Furthermore, this invention uses a transverse self-stressing joint to connect the two-way prestressed concrete slab and the reinforced concrete slab. This transverse self-stressing joint itself has a certain self-stress. During the pouring process of the self-stressing joint, the high-expansion concrete expands while simultaneously applying a gradually decreasing compressive stress to the ordinary concrete slab end. This solves both the problem of insufficient overall strength of ordinary connection joints and the problem of uniform transition from stress to stresslessness in the longitudinal direction of the approach slab. Simultaneously, this invention uses a longitudinal hinged connection joint to connect the left and right precast slabs. Only shear force is transferred between the two slabs, not bending moment, resulting in a clear stress distribution and significantly reducing the transverse reinforcement of the left and right slabs.

[0063] While exemplary embodiments and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made to these embodiments without departing from the spirit of the invention and the scope of protection defined by the appended claims. For other examples, those skilled in the art should readily understand that the order of process steps can be varied while remaining within the scope of the invention.

[0064] Furthermore, the scope of this invention is not limited to the processes, mechanisms, manufacturing methods, material compositions, means, methods, and steps of the specific embodiments described in the specification. From the disclosure of this invention, those skilled in the art will readily understand that any existing or future processes, mechanisms, manufacturing methods, material compositions, means, methods, or steps that perform substantially the same function or obtain substantially the same results as the corresponding embodiments described in this invention can be applied according to this invention. Therefore, the appended claims are intended to include these processes, mechanisms, manufacturing methods, material compositions, means, methods, or steps within their scope of protection.

Claims

1. A structure for an ultra-long approach slab in a high-fill roadbed, suitable for the design and construction of ultra-long approach slabs in high-fill roadbeds, characterized in that: The structure is composed of bidirectional prestressed concrete slab, reinforced concrete slab and connecting joint; The bidirectional prestressed concrete slab is composed of concrete, longitudinal double-layer and single-layer transverse prestressed reinforcement; The reinforced concrete slab is composed of concrete and HRB335 steel reinforcement arranged in double layers in the vertical and horizontal directions; The connecting joint is composed of transverse self-stress joint and longitudinal hinge connecting joint; The arrangement structure of the three parts of the deck slab is as follows: the bidirectional prestressed concrete slab is arranged in two parts on the left and right sides near the abutment end, the width and thickness of the reinforced concrete slab on the left and right sides are the same as the width and thickness of the corresponding bidirectional prestressed concrete slab in the longitudinal direction, and the reinforced concrete slab is arranged far from the abutment end, the bidirectional prestressed concrete slab and the reinforced concrete slab are connected and transitioned by the transverse self-stress joint, and the bidirectional prestressed concrete slab and the reinforced concrete slab are connected by the longitudinal hinge connecting joint; the longitudinal hinge connecting joint is continuous in the longitudinal direction of the deck slab, and the transverse self-stress joint is spaced apart from the left and right joints at the intersection with the longitudinal hinge connecting joint.

2. The structure of the high fill subgrade super-long bridging slab according to claim 1, characterized in that: The center line of the longitudinal hinge connecting joint coincides with the position of the marking line arranged between the driving lane and the overtaking lane on the deck slab; and the position of the transverse self-stress joint matches the length of the bidirectional prestressed concrete slab.

3. The structure of the high fill subgrade super-long shoring board according to claim 1, characterized in that: The length of the bidirectional prestressed concrete slab matches the expected overhanging length in the design life of the road under the deck slab, the bidirectional prestressed concrete slab is arranged in double rows in the vertical direction and symmetrically, and a single row of prestressed reinforcement is arranged in the middle of the bidirectional prestressed concrete slab in the transverse direction.

4. The structure of the high fill subgrade super-long shoring board according to claim 1, characterized in that: The transverse self-stress joint is composed of high-expansion concrete, longitudinal self-stress reinforcement and self-stress joint transverse reinforcement, the joint width is 22-30 cm, the high-expansion concrete has the same mark as the concrete of the deck slab and has a strength of 40-45 MPa; the longitudinal self-stress reinforcement is double layers of HRB335 steel reinforcement arranged symmetrically in the longitudinal self-stress joint and embedded in the bidirectional prestressed concrete slab and the reinforced concrete slab one by one.

5. The structure of the super-long tie-plate of high fill subgrade according to claim 4, characterized in that: The self-stress joint transverse reinforcement is double rows of HRB335 steel reinforcement arranged in the longitudinal self-stress joint, and the upper and lower self-stress joint transverse reinforcement is bound on the longitudinal self-stress reinforcement at equal intervals.

6. The structure of the high fill subgrade super-long shoring board according to claim 1, characterized in that: The longitudinal hinge connecting joint is composed of micro-expansion concrete, tension reinforcement, anti-rust paint and pre-cut joint, the joint width is 12-15 cm, and the micro-expansion concrete has a strength of 40-45 MPa; the tension reinforcement is embedded in the bidirectional prestressed concrete slab and the reinforced concrete slab, and the embedded position is in the middle of the bidirectional prestressed concrete slab; the anti-rust paint is in the middle of the tension reinforcement; and the pre-cut joint is on the center line of the longitudinal hinge connecting joint.

7. A method of constructing the structure of the super-long tie plate of the high fill subgrade according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: 1) prefabrication: two steel formworks are arranged on the left and right sides according to the size of the bidirectional prestressed concrete slab and the reinforced concrete slab; the longitudinal and transverse corrugated pipes of the bidirectional prestressed concrete slab and the longitudinal and transverse double-layer steel reinforcement of the reinforced concrete slab are fixed, the longitudinal self-stress reinforcement and the transverse tension reinforcement are embedded, the concrete is poured, the vibrating rod is vibrated, the surface is smoothed by the surface grinder, and the curing cloth is covered and water is sprayed for curing for seven days; 2) Tensioning and grouting of two-way prestressed concrete slab: the concrete strength of two-way prestressed concrete slab reaches 100% of the design strength, steel strand is inserted into the bellows, the steel strand is tensioned to the design value, cement concrete grout is pressed into the bellows, and the anchor is sealed; 3) Installation: double-layer oil felt is laid on the corbel, two-way prestressed concrete slab and reinforced concrete slab are installed according to the reserved position of the connecting joint in sequence, and anchor bolts are installed to anchor the lapping plate on the corbel; 4) Construction of transverse self-stress joint: longitudinal self-stress reinforcement is connected, the welding length is not less than 10 times the diameter, and transverse reinforcement is bound; high-expansion concrete is poured, and water curing is maintained for seven days; 5) Construction of longitudinal hinge-type connecting joint: transverse tensioning reinforcement is connected, double-sided welding length is not less than 5 times the diameter; anti-rust paint is brushed at 8cm-10cm of the middle part of the tensioning reinforcement, micro-expansion concrete is poured, and moisture-proof cotton curing is maintained for seven days; a pre-cut joint is cut at the center line of the longitudinal hinge-type connecting joint by using a concrete cutting machine, and petroleum asphalt is poured.

Images